High-performance thin-film Li4Ti5O12 electrodes fabricated by using ink-jet printing technique and their electrochemical properties

Li₄Ti₅O₁₂ thin-film anode with high discharge capacity and excellent cycle stability for rechargeable lithium ion batteries was prepared successfully by using ink-jet printing technique. The prepared Li₄Ti₅O₁₂ thin film were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, cyclic voltammograms, and galvanostatic charge–discharge measurements. It was found that the average thickness of 10-layer Li₄Ti₅O₁₂ film was about 1.7~1.8 μm and the active material Li₄Ti₅O₁₂ in the thin film was nano-sized about 50–300 nm. It was also found that the prepared Li₄Ti₅O₁₂ thin film exhibited a high discharge capacity of about 174 mAh/g and the discharge capacity in the 300th cycle retained 88% of the largest discharge capacity at a current density of 10.4 μA/cm² in the potential range of 1.0–2.0 V.     

Synthesis and electrochemical performances of Li4Ti4.95Zr0.05O12/C as anode material for lithium-ion batteries

Spinel Li₄Ti_5 − x Zr _x O₁₂/C (x = 0, 0.05) were prepared by a solution method. The structure and morphology of the as-prepared samples were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The electrochemical performances including charge–discharge (0–2.5 V and 1–2.5 V), cyclic voltammetry, and ac impedance were also investigated. The results revealed that the Li₄Ti_4.95Zr_0.05O₁₂/C had a relatively smaller particle size and more regular morphology than that of Li₄Ti₅O₁₂/C. Zr⁴⁺ doping enhanced the ability of lithium-ion diffusion in the electrode. It delivered a discharge capacity 289.03 mAh g⁻¹ after 50 cycles for the Zr⁴⁺-doped Li₄Ti₅O₁₂/C while it decreased to 264.03 mAh g⁻¹ for the Li₄Ti₅O₁₂/C at the 0.2C discharge to 0 V. Zr⁴⁺ doping did not change the electrochemical process, instead enhanced the electronic conductivity and ionic conductivity. The reversible capacity and cycling performance were effectively improved especially when it was discharged to 0 V.     

Study of capacitive properties for LT-Li4Mn5O12 in hybrid supercapacitor

Spinel Li₄Mn₅O₁₂ nanoparticles have been prepared by a very simple sol–gel method. Various initial conditions were studied in order to find the optimal conditions for the synthesis of pure Li₄Mn₅O₁₂. X-ray diffraction results showed that spinel Li₄Mn₅O₁₂ was obtained at a low temperature of 300 °C without any miscellaneous phase. Scanning electron microscope analyses indicated that the prepared Li₄Mn₅O₁₂ powders had a uniform morphology with average particle size of about 50 and 100 nm. The prepared sample was firstly used as a cathode material in an asymmetric Li₄Mn₅O₁₂/AC supercapacitor in aqueous electrolyte. The capacitive properties of the hybrid supercapacitor were tested by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge–discharge tests. The results showed that Li₄Mn₅O₁₂ annealed at 450 °C for 4 h exhibited the best electrochemical capacitive performance within the potential range of 0–1.4 V in 1 M Li₂SO₄ solution. A maximum specific capacitance of 43 F g⁻¹ based on the total active material weight of the two electrodes was obtained for the Li₄Mn₅O₁₂/AC supercapacitor at a current density of 100 mA g⁻¹. The capacitor showed excellent cycling performance and structure stability via 1,000 cycles.     

Effect of Nb-doping on electrochemical stability of Li4Ti5O12 discharged to 0?V

Li₄Ti_4.95Nb_0.05O₁₂ is synthesized by a citric acid-assistant sol–gel method. X-ray diffraction (XRD) reveals that highly crystalline Li₄Ti_4.95Nb_0.05O₁₂ without any impurity is obtained. The electrochemical performances of the Li₄Ti_4.95Nb_0.05O₁₂ and the Li₄Ti₅O₁₂ in the range from 0 to 2.5 V are investigated. The Li₄Ti_4.95Nb_0.05O₁₂ presents a higher specific capacity and better cycling stability than the Li₄Ti₅O₁₂ due to the improved conductivity. The Li₄Ti_4.95Nb_0.05O₁₂ exhibits a capacity as high as 231.2 mAh g⁻¹ after 100 cycles, which is much higher than the Li₄Ti₅O₁₂ (111.1 mAh g⁻¹). The effect of Nb-doping on electrochemical performance of Li₄Ti₅O₁₂ discharged to 0 V has also been discussed.     

Li ion diffusion in Li4Ti5O12 thin film electrode prepared by PVP sol-gel method

Li₄Ti₅O₁₂ thin films for rechargeable lithium batteries were prepared by a sol-gel method with poly(vinylpyrrolidone). Interfacial properties of lithium insertion into Li₄Ti₅O₁₂ thin film were examined by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and potentiostatic intermittent titration technique (PITT). Redox peaks in CV were very sharp even at a fast scan rate of 50 mV s⁻¹, indicating that Li₄Ti₅O₁₂ thin film had a fast electrochemical response, and that an apparent chemical diffusion coefficient of Li⁺ ion was estimated to be 6.8×10⁻¹¹ cm² s⁻¹ from a dependence of peak current on sweep rates. From EIS, it can be seen that Li⁺ ions become more mobile at 1.55 V vs. Li/Li⁺, corresponding to a two-phase region, and the chemical diffusion coefficients of Li⁺ ion ranged from 10⁻¹⁰ to 10⁻¹² cm² s⁻¹ at various potentials. The chemical diffusion coefficients of Li⁺ ion in Li₄Ti₅O₁₂ were also estimated from PITT. They were in a range of 10⁻¹¹-10⁻¹² cm² s⁻¹.     

Electrochemical characteristics of spinel Li4Ti5O12 discharged to 0.01 V

Cycling stability, reversible capacity and rate performance of Li₄Ti₅O₁₂ discharged to 0.01 V were investigated. A couple of obvious and repeatable peaks under 0.6 V observed by CV indicated that Li₄Ti₅O₁₂ possessed reversible capacity below 0.6 V. When discharge voltage of Li₄Ti₅O₁₂ extended from 0.6 to 0.01 V, its cycling stability was not affected and its reversible capacity and high rate performance were improved. Although the capacity obtained from 2.0 to 0.6 V gradually decreased with increasing the applied current density, the capacity obtained from 0.6 to 0.01 V showed little loss. AB was both electronic conducting additive and lithium-ion conducting additive for Li₄Ti₅O₁₂ under 0.6 V.     

Li4Ti5O12/(Ag+C)电极材料的固相合成及电化学性能

以Li₂CO₃,TiO₂为原料,葡萄糖为碳源,采用固相煅烧工艺合成了亚微米级的Li₄Ti₅O₁₂/C复合负极材料。并将之与AgNO₃复合,采用固相方法制备出了Ag表面修饰的Li₄Ti₅O₁₂/(Ag+C)复合材料。采用XRD、SEM和TEM测试方法对材料的微结构进行了表征。结果表明,C的存在对Ag单质在Li₄Ti₅O₁₂/C颗粒表面的大量形成起到了积极的促进作用,从而很大程度地提高了Li₄Ti₅O₁₂/C的电导率,因此有效地改善了其电化学性能。在1C倍率下,Li₄Ti₅O₁₂/(Ag+C)复合材料的首次放电容量达到了164 mAh·g^-1。     

三维连续结构Li4Ti5O12/石墨烯纳米复合材料：制备和其锂离子电池超长循环性能

利用具有三维连续纳米孔结构的热剥离石墨烯为骨架制备Li4Ti5O12/石墨烯纳米复合材料。通过乙醇挥发法在热剥离石墨烯的纳米孔道内引入前驱物,进一步高温热处理,在热剥离石墨烯的孔道内原位形成Li4Ti5O12纳米粒子。利用复合材料作为锂离子电池电极材料。电化学反应过程中,热剥离石墨烯的三维连续结构确保了Li4Ti5O12纳米粒子与石墨烯在长循环过程中的有效接触。因此,复合材料表现出优异的循环稳定性。在5C下,5 000次循环后,其容量保持率高达94%。     

Preparation and characterization of nanotube Li-Ti-O by molten salt method

Nanotube Li-Ti-O compound with high surface (198.6 m²·g⁻¹) was prepared by a method involving the treatment of nanotube Na₂Ti₂O₅·H₂O in molten LiNO₃ and characterization by means of transmission electron microscopy (TEM), energy-dispersive spectra (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and thermogravimetry-differential thermal analysis (TG/DTG). Results show that the nanotube Li-Ti-O compound prepared by this method involves two crystal phases: spinel Li₂Ti₂O₄ and anatase Li_xTiO₂ (x < 0.1). Li⁺ exhibits different Li1s binding energy in the two crystal phases. In ambient air, the Li-Ti-O compound adsorbs water easily, and the chemically adsorbed water is difficult to remove below 400°C. Translated from Chinese Journal of Inorganic Chemistry, 2006, 22(12): 2135–2139 [译自: 无机化学学报]     

Comparison of structure and electrochemical properties for 5 V LiNi0.5Mn1.5O4 and LiNi0.4Cr0.2Mn1.4O4 cathode materials

Spinel LiNi_0.5Mn_1.5O₄ and LiMn_1.4Cr_0.2Ni_0.4O₄ cathode materials have been successfully synthesized by the sol–gel method using citric acid as a chelating agent. The structure and electrochemical performance of these as-prepared powders have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and the galvanostatic charge–discharge test in detail. XRD results show that there is a small Li _y Ni_1-y O impurity peak placed close to the (4 0 0) line of the spinel LiNi_0.5Mn_1.5O₄, and LiMn_1.4Cr_0.2Ni_0.4O₄ has high phase purity, and the powders are well crystallized. SEM indicates that LiMn_1.4Cr_0.2Ni_0.4O₄ has a slightly smaller particle size and a more regular morphological structure with narrow size distribution than those of LiNi_0.5Mn_1.5O₄. Galvanostatic charge–discharge testing indicates that the initial discharge capacities of LiMn_1.4Cr_0.2Ni_0.4O₄ and LiNi_0.5Mn_1.5O₄ cycled at 0.15 C are 129.6 and 130.2 mAh g⁻¹, respectively, and the capacity losses compared to the initial value, after 50 cycles, are 2.09% and 5.68%, respectively. LiMn_1.4Cr_0.2Ni_0.4O₄ cathode has a higher electrode coulombic efficiency than that of the LiNi_0.5Mn_1.5O₄ cathode, implying that Ni and Cr dual substitution is beneficial to the reversible intercalation and de-intercalation of Li⁺.     

Synthesis and electrochemical properties of Ca-doped LiNi<Subscript>0.8</Subscript>Co<Subscript>0.2</Subscript>O<Subscript>2</Subscript> cathode material for lithium ion battery

LiNi_0.8Co_0.2O₂ and Ca-doped LiNi_0.8Co_0.2O₂ cathode materials have been synthesized via a rheological phase reaction method. X-ray diffraction studies show that the Ca-doped material, and also the discharged electrode, maintains a hexagonal structure even when cycled in the range of 3.0–4.35 V (vs Li⁺/Li) after 100 cycles. Electrochemical tests show that Ca doping significantly improves the reversible capacity and cyclability. The improvement is attributed to the formation of defects caused by the partial occupancy of Ca²⁺ ions in lithium lattice sites, which reduce the resistance and thus improve the electrochemical properties.     

Improvement of overcharge performance using Li4Ti5O12 as negative electrode for LiFePO4 power battery

Liquid state soft packed LiFePO₄ cathode lithium ion cells with capacity of 2 Ah were fabricated using graphite or Li₄Ti₅O₁₂ as negative electrodes to investigate the 3 C/10 V overcharge characteristics at room temperature. The LiFePO₄/Li₄Ti₅O₁₂ cell remained safe after the 3 C/10 V overcharge test while the LiFePO₄/graphite cell went to thermal runaway. Temperature and voltage variations during overcharge were recorded and analyzed. The cells after overcharge were disassembled to check the changes of the separated cell components. The results showed that the Li₄Ti₅O₁₂ as anode active material for LiFePO₄ cell showed obvious safety advantage compared with the graphite anode. The lithium ionic diffusion models of Li₄Ti₅O₁₂ anode and graphite anode were built respectively with the help of morphology characterizations performed by scanning electron microscopy. It was found that the different particle shapes and lithium ionic diffusion modes caused different lithium ionic conductivities during overcharge process.     

Synthesis and electrochemical properties of spinel Li4Ti5O12−x Cl x anode materials for lithium-ion batteries

Li₄Ti₅O_12−x Cl _x (0 ≤ x ≤ 0.3) compounds were synthesized successfully via high temperature solid-state reaction. X-ray diffraction and scanning electron microscopy were used to characterize their structure and morphology. Cyclic voltammetry, electrochemical impedance spectroscopy, and charge/discharge cycling performance tests were used to characterize their electrochemical properties. The results showed that the Li₄Ti₅O_12−x Cl _x (0 ≤ x ≤ 0.3) compounds were well-crystallized pure spinel phase and that the grain sizes of the samples were about 3–8 μm. The Li₄Ti₅O_11.8Cl_0.2 sample presented the best discharge capacity among all the samples and showed better reversibility and higher cyclic stability compared with pristine Li₄Ti₅O₁₂. When the discharge rate was 0.5 C, the Li₄Ti₅O_11.8Cl_0.2 sample presented the superior discharge capacity of 148.7 mAh g⁻¹, while that of the pristine Li₄Ti₅O₁₂ was 129.8 mAh g⁻¹; when the discharge rate was 2 C, the Li₄Ti₅O_11.8Cl_0.2 sample presented the discharge capacity of 120.7 mAh g⁻¹, while that of the pristine Li₄Ti₅O₁₂ was only 89.8 mAh g⁻¹.     

LiMn2O4表面包覆Li4Ti5O12的制备及倍率特性

采用固相法合成了尖晶石型LiMn₂O₄，并通过溶胶-凝胶法制备了不同物质的量的百分比含量Li₄Ti₅O₁₂包覆的正极材料。X-射线衍射和扫描电镜结果表明，Li₄Ti₅O₁₂微粒包覆在LiMn₂O₄的表面没有产生晶体结构的变化。实验电池在室温下，以1C，2C和5C倍率作充放电循环测试；结果表明，与未包覆的LiMn₂O₄相比，表面包覆Li₄Ti₅O₁₂微粒的正极材料在高倍率下具有更好的循环稳定性。     

Effect of surface fluorination and conductive additives on the electrochemical behavior of lithium titanate (Li4/3Ti5/3O4) for lithium ion battery

Effect of surface fluorination and conductive additives on the charge/discharge behavior of lithium titanate (Li_4/3Ti_5/3O₄) has been investigated using F₂ gas and vapor grown carbon fiber (VGCF). Surface fluorination of Li_4/3Ti_5/3O₄ was made using F₂ gas (3 × 10⁴ Pa) at 25-150 °C for 2 min. Charge capacities of Li_4/3Ti_5/3O₄ samples fluorinated at 70 °C and 100 °C were larger than those for original sample at high current densities of 300 and 600 mA/g. Optimum fluorination temperatures of Li_4/3Ti_5/3O₄ were 70 °C and 100 °C. Fibrous VGCF with a large surface area (17.7 m²/g) increased the utilization of available capacity of Li_4/3Ti_5/3O₄ probably because it provided the better electrical contact than acetylene black (AB) between Li_4/3Ti_5/3O₄ particles and nickel current collector.     

Preparation and electrochemical performance of monodisperse Li4Ti5O12 hollow spheres

Monodisperse Li₄Ti₅O₁₂ hollow spheres were prepared by using carbon spheres as templates. Scanning electron microscopy images show hollow spheres that have an average outer diameter of 1.0 μm and an average wall thickness of 60 nm. Compared with Li₄Ti₅O₁₂ solids, the hollow spherical Li₄Ti₅O₁₂ exhibit an excellent rate capability and capacity retention and can be charged/discharged at 10 C (1.7 A g⁻¹) with a specific capacity of 100 mA h g⁻¹, and after 200 charge and discharge cycles at 2 C, their specific capacity remain very stable at 150 mA h g⁻¹. It is believed that the hollow structure has a relatively large contact surface between Li₄Ti₅O₁₂ and liquid electrolyte, resulting in a better electrochemical performance at high charge/discharge rate.     

Li4Ti5O12/(Cu+C)复合材料的制备及电化学性能

以Li₄Ti₅O₁₂,Cu(CH₃COO)₂·H₂O和C₆H₁₂O₆为前驱体,化学沉积与热分解结合合成锂离子电池负极材料Li₄Ti₅O₁₂/(Cu+C)。采用X-射线衍射(XRD)、扫描电子显微镜(SEM)、恒流充放电、循环伏安和电化学阻抗方法表征样品的结构、形貌和电化学性能。结果表明,Li₄Ti₅O₁₂表面包覆的Cu与C提高了Li₄Ti₅O₁₂电极材料的导电率,其循环性能和倍率性能得到有效地改善。在0.5C、1C和3C倍率下,经过50次充放电循环,放电比容量分别为168.2、160、140.6 mAh·g^-1,其容量保持率分别为88.7%、84.4%、71.2%。电化学阻抗测试表明,表面包覆的Cu与C使其电荷转移阻抗大幅度减少。     

Phase-pure nanocrystalline Li<Subscript>4</Subscript>Ti<Subscript>5</Subscript>O<Subscript>12</Subscript> for a lithium-ion battery

Phase-pure nanocrystalline Li₄Ti₅O₁₂ with BET surface areas between 183 and 196 m²/g was prepared via an improved synthetic protocol from lithium ethoxide and titanium(IV) butoxide. The phase purity was proved by X-ray powder diffraction, Raman spectroscopy and cyclic voltammetry. Thin-film electrodes were prepared from two nanocrystalline samples of Li₄Ti₅O₁₂ and one microcrystalline commercial sample. Li-insertion behavior of these electrodes was related to the particle size.Presented at the 3rd International Meeting on Advanced Batteries and Accumulators, 16–20 June 2002, Brno, Czech Republic     

Li4Ti5O12 Anode: Structural Design from Material to Electrode and the Construction of Energy Storage Devices

Spinel Li₄Ti₅O₁₂, known as a zero‐strain material, is capable to be a competent anode material for promising applications in state‐of‐art electrochemical energy storage devices (EESDs). Compared with commercial graphite, spinel Li₄Ti₅O₁₂ offers a high operating potential of ∼1.55 V vs Li/Li⁺, negligible volume expansion during Li⁺ intercalation process and excellent thermal stability, leading to high safety and favorable cyclability. Despite the merits of Li₄Ti₅O₁₂ been presented, there still remains the issue of Li₄Ti₅O₁₂ suffering from poor electronic conductivity, manifesting disadvantageous rate performance. Typically, a material modification process of Li₄Ti₅O₁₂ will be proposed to overcome such an issue. However, the previous reports have made few investigations and achievements to analyze the subsequent processes after a material modification process. In this review, we attempt to put considerable interest in complete device design and assembly process with its material structure design (or modification process), electrode structure design and device construction design. Moreover, we have systematically concluded a series of representative design schemes, which can be divided into three major categories involving: (1) nanostructures design, conductive material coating process and doping process on material level; (2) self‐supporting or flexible electrode structure design on electrode level; (3) rational assembling of lithium ion full cell or lithium ion capacitor on device level. We believe that these rational designs can give an advanced performance for Li₄Ti₅O₁₂‐based energy storage device and deliver a deep inspiration.     

Sulfone-based electrolytes for high-voltage Li-ion batteries

Sulfone-based electrolytes have been investigated as electrolytes for lithium-ion cells using high-voltage positive electrodes, such as LiMn₂O₄ and LiNi_0.5Mn_1.5O₄ spinels, and Li₄Ti₅O₁₂ spinel as negative electrode. In the presence of imide salt (LiTFSI) and ethyl methyl sulfone or tetramethyl sulfone (TMS) electrolytes, the Li₄Ti₅O₁₂/LiMn₂O₄ cell exhibited a specific capacity of 80 mAh g^?1 with an excellent capacity retention after 100 cycles. In a cell with high-voltage LiNi_0.5Mn_1.5O₄ positive electrode and 1 M LiPF₆ in TMS as electrolyte, the capacity reached 110 mAh g^?1 at the C/12 rate. When TMS was blended with ethyl methyl carbonate, the Li₄Ti₅O₁₂/LiNi_0.5Mn_1.5O₄ cell delivered an initial capacity of 80 mAh g^?1 and cycled fairly well for 1000 cycles under 2C rate. The exceptional electrochemical stability of the sulfone electrolytes and their compatibility with the Li₄Ti₅O₁₂ safer and stable anode were the main reason behind the outstanding electrochemical performance observed with high-potential spinel cathode materials. These electrolytes could be promising alternative electrolytes for high-energy density battery applications such as plug-in hybrid and electric vehicles that require a long cycle life.